1. Field of the Invention
The present invention relates to a method and an apparatus for tuning an analog filter, and more particularly, to a method and an apparatus for tuning parameter settings of an analog filter using output data.
2. Description of the Prior Art
In data access systems, multiple bits of a digital signal are encoded as a symbol for increasing the transmission bit rate and reducing bit error rates caused by noise. For example, the run-length limited (RLL) code is used for encoding in compact discs (CDs) or digital video discs (DVDs) systems. RLL(n, k) indicates that a symbol is composed of a serious of 1 or 0 in length of (n+1) to (k+1). Each bit of the digital signals is recorded in the form of pit/lands on the discs and is accessed by laser-light spot in the CD/DVD systems. However, the laser-light spot covers several pits/lands and generates inter-symbol interference (ISI), which leads to a serious bit error rate and affects the performance of data access systems. Generally speaking, the receiver of a data access system uses an analog filter to filter the received symbols, which reduces the ISI to lower the bit error rate. Thus, performance of the analog filter affects the performance of the data access system.
Parameter settings of the analog filter affect the performance of the analog filter. For example, the jitter of accessing signals corresponds to a parameter setting of the analog filter. Thus, the prior art manufacturers use different parameters to tune the analog filter. Because the parameter settings of the analog filter correspond to the brand or type of the disc machine including the analog filter, the prior art method of tuning the analog filter repeatedly uses a manual trial-and-error mechanism to find the best parameters corresponding to the analog filter of the disk machine. Thus, manufacturers make efforts to find the best parameters according to the analog filter of each disc machine.